Ethylene oxide (EO) is a product manufactured worldwide in amounts of several million tonnes per year. The production of EO is described, for example, in Kirk-Othmer Encyclopaedia of Chemical Technology, third edition, Volume 9, 1980, pages 443 to 447.
A conventional EO distillation system is discussed in WO2006/120207, e.g. with reference to FIG. 1 therein. In a conventional system, loopgas from an EO reactor is passed to a loopgas EO absorber where it is absorbed by an aqueous lean absorbent (LA) to form fat absorbent (FA).
The FA then enters a stripper column in which heat is supplied, typically by steam or a reboiler, to produce overhead vapours comprising EO and a bottoms LA stream for recycling. The overhead vapours are condensed and/or reabsorbed to form a stripped, concentrated EO stream.
Where purified EO is required, there follows purification of the stripped EO stream by distillation.
Purification is generally performed in one or more distillation columns. Such columns vary in design but inevitably require reheating of the condensed EO stream to effect distillation. Indeed, in some systems multiple cycles of reheating and condensation occur before EO purification is complete.
Prior art processes for recovering EO, in particular high purity EO comprising at least 99.5 wt % EO, are energy intensive as a result of the heating, condensation and reheating that occurs during stripping and purification. Nevertheless, the traditional approach of stripping followed by purification is engrained in the art.
U.S. Pat. No. 4,134,797A describes a process for recovering ethylene oxide containing low levels of aldehyde impurities using a multi-stage countercurrent distillation zone.
U.S. Pat. No. 4,033,617A describes a process for purifying an aqueous stream containing absorbed ethylene oxide and acetaldehyde, comprising condensations, liquefaction and distillation steps.
It is an object of the invention to provide a more energy efficient solution for recovering EO from FA and/or to solve at least one problem associated with the prior art.